Device for turning sheet-like substrates

ABSTRACT

A turning unit for sheet-like substrates has at least one first turning element with a basic body having an outer, round substrate contact surface for deflecting the substrate. The deflection is from a first sheet conveying direction to a second sheet conveying direction describing a predetermined angle to the first sheet conveying direction. Furthermore, a channel structure is provided that is formed in the substrate contact surface and onto which open a plurality of gas outlet openings which are in fluid communication with a gas supply.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a device for turning sheet-likesubstrates, in particular sheet-like substrates in a printing press,that are to undergo verso printing following recto printing.

BACKGROUND OF THE INVENTION

In printing technology, turning units are known which following rectoprinting use deflecting elements to turn sheet-like print materials forverso printing. A turning unit of this type is described for example inDE 43 35 473. The turning unit described there has two fixed turningelements rotated 90° to one another and a deflecting element positionedin a sheet running direction between the turning elements. The turningelements are each inclined 45° to a running direction of a substratesheet, as a result of which they each provide a 90° turn.

The turning elements can guide the substrate sheet in a sliding andcontacting manner, or, as described in DE 43 35 473, over an air cushionbetween the substrate sheet and the turning element. To generate the aircushion, the turning elements are provided with a cavity and a pluralityof openings connected to said cavity and opening onto the circumferenceof the turning element. To generate an air cushion between the substratesheet and the turning element which reduces the friction between them,the cavity is supplied with compressed air which exits through theopenings in the turning elements.

A drawback of a design of this type is the high air consumption neededto generate a sufficient air cushion over the width of a substratesheet. A high air consumption of this nature is concomitant withcorrespondingly high energy consumption for generating the required airquantity. In edge areas of the substrate sheet, there fluttering of thesubstrate sheet may also result from high air flows, which can impairthe guidance accuracy of the substrate sheet. Furthermore, a heavy noisedevelopment can result from this and/or from strong air flows.

The printing of sheet-like print materials requires a high degree ofaccuracy in respect of the guidance of the print material. The guidanceaccuracy can be impaired by repeated turning of print material sheets ina turning unit of the above type.

SUMMARY OF THE INVENTION

The object underlying the present invention is to provide a device forturning a sheet-like substrate of the above type and for eliminating atleast one of the aforementioned drawbacks, in particular permittinglower air consumption for generating the air cushion.

In accordance with the invention, this object is achieved by a turningunit according to claim 1. Further embodiments of the invention aredetailed in the respective sub-claims.

In particular, a turning unit for sheet-like substrates is provided withat least one first turning element having a basic body with an outer,round substrate guide surface angled relative to a sheet conveyingdirection.

Furthermore provided are a channel structure that is formed in thesubstrate guide surface, and a plurality of gas outlet openings openingonto the channel structure and which can be supplied with gas in orderto provide a gas flow to the channel structure.

The channel structure in the substrate guide surface permits an improvedand more even distribution of air between the turning element and asubstrate sheet passing over it. As a result, the air quantity used andhence the energy expended to form a sufficient air cushion can bereduced. As a result, low noise development can be achieved. Inparticular in edge areas of the substrate sheet, the channel structurecan provide a controlled air flow, as a result of which fluttering ofthe substrate sheet and the associated noise development can ifnecessary be reduced. The first turning element can for example bearranged fixed at a 45° angle to a first sheet conveying direction,where said first sheet conveying direction is the sheet runningdirection of the substrate sheet before it is turned by the turningelement. This would result in a 90° turn relative to the first sheetconveying direction.

In a preferred embodiment, at least two turning elements are providedwhich are each arranged at an angle to a sheet conveying direction andalso relative to one another. As a result, a double turn of thesubstrate sheet and hence for example a 180° turn can be provided. Theturning elements can be arranged in the known manner each at 45° to thesheet conveying direction and intersecting one another at a 90° angle.In a sheet running direction, a pivot-mounted intermediate roller can beprovided between the turning elements, by which the sheet-like printmaterial is deflected after the first turn to the second turningelement. An arrangement of this type permits in known manner a compactarrangement of the turning unit.

In an embodiment of the invention, the channel structure inside thesubstrate contact surface has a plurality of circumferential channelsspaced apart and extending in the circumferential direction of the roundsubstrate guide surface, and at least one transverse channel extendingtransversely to the circumferential channels and being in fluidcommunication with at least two circumferential channels. As a result, agood distribution of air can be achieved between the turning element andthe substrate sheet. The at least one transverse channel can here extendin the circumferential direction of the circumferential channels andcentrally thereto. The circumferential channels preferably each have thesame distances relative to one another. However, another arrangement ofthe circumferential channels can also be provided. With an arrangementof this type of the circumferential channels and of the at least onetransverse channel, supplied gas or air can easily be distributed in therespective channels, thereby achieving an even air cushion between theturning element and the substrate sheet.

In one embodiment, at least some of the gas outlet openings open onto atleast one transverse channel in order to provide a good distribution ofsupplied gas over a width of a substrate sheet.

In an alternative embodiment, the channel structure has channelsdistributed statistically in the substrate contact surface. As a result,a particularly even distribution of supplied gas can be achieved overthe substrate guide surface.

Preferably, a control unit is provided which is able to supply gas tothe gas outlet openings individually or in groups. This makes itpossible to supply gas substantially only to those gas outlet openingswhich are covered during operation by a substrate sheet in order toreduce leakage flows. An adaptation to differing widths of substratesheets is thus possible. As a result, the entire air quantity and anenergy consumption connected thereto, and if applicable also the noisedevelopment, can be reduced.

In an embodiment, a cavity is provided inside the basic body of theturning element which is in fluid communication with the gas outletopenings and which can be supplied with gas. A cavity of this typepermits a particularly simple supply of gas to the gas outlet openings.It can for example be subdivided in order to achieve easily by thissubdivision an individual or grouped controllability of the gas outletopenings. Inside the cavity, a slider can also be movably mounted suchthat it permits selective supplying of gas to gas outlet openings viathe cavity. A slide of this type permits a continuous adjustment of thearea of the cavity via which gas outlet openings can be supplied withgas. This permits an approximately continuous adjustment to the width ofa substrate sheet. Two slides can be provided here that are movable fromopposite ends into the cavity to permit an adjustment to a position andwidth of the substrate sheet.

Alternatively or additionally, a plurality of valves can also beprovided for individual or grouped supplying of gas to gas outletopenings.

The substrate guide surface can have a plurality of separate channelstructure segments arranged adjacently over a width of the substrateguide surface, where a respective channel structure is in fluidcommunication with at least one gas outlet opening. The individualchannel structure segments could each be separated from one another byareas without channels of the substrate guide surface. The respectivechannel structure segments are preferably thus not in fluidcommunication with one another via channels. An arrangement of this typeof channel structure segments permits ready adjustment to the width of asheet-like substrate in particular with a segment-by-segment supply tothe gas outlet openings. The separation of the channel structuresegments allows a reduction of leakage flows via the respective channelstructure. Preferably, gas inlet opening(s) associated with a respectivechannel structure segment can be supplied with gas in groups.

The channels preferably extend over a maximum of 180° in thecircumferential direction of the substrate guide surface in order toreduce leakage flows. In particular, the channels should extend in thecircumferential direction of the substrate guide surface at most overone winding area of the substrate sheet.

In accordance with a preferred embodiment, the channel structure has adepth of 0.1 to 1 mm, which on the one hand permits a good distributionof gas and on the other hand prevents excessive leakage flows. Thechannel structure can for example be provided in the surface of thebasic body by milling, etching or with the aid of lasers. It can ofcourse also be formed in other ways. The gas outlet openings preferablyhave a diameter of 0.3 to 0.5 mm.

Furthermore, a device for printing on a substrate sheet is providedwhich has at least one printing unit for application of a print mediumonto the substrate sheet and a turning unit of the above type.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained in more detail in the following withreference to the drawings, which show in:

FIG. 1 a schematic side view of a printing press with turning unit inaccordance with the invention;

FIG. 2 a schematic detailed view of a turning unit in accordance withthe invention with two turning elements and one intermediate roller;

FIG. 3 a schematic plan view onto a movement area of a substrate sheetin the view from line A in FIG. 1;

FIG. 4 a schematic plan view onto a turning element in accordance withthe invention;

FIG. 5 a schematic plan view onto an alternative turning element inaccordance with the invention;

FIG. 6 a schematic detailed view of a channel structure in a surface ofa turning element in accordance with an embodiment of the invention;

FIG. 7 a schematic sectional view through the turning element inaccordance with FIG. 6 along the line B-B in FIG. 6; and

FIG. 8 a schematic detailed view of a channel structure in a surface ofa turning element in accordance with an alternative embodiment of theinvention.

DETAILED DESCRIPTION OF THE INVENTION

The position and direction information provided in the followingdescription relates primarily to the illustrations in the drawings andshould therefore not be deemed to be restrictive. It can however alsorelate to a preferred final arrangement.

FIG. 1 shows a schematic side view of a printing press 1 with afeeder/delivery area 2, a print area 3 and a turning area 4. The printarea 3 is arranged between the feeder/delivery area 2 and the turningarea 4.

In the feeder/delivery area 2, a first print material roll 5 is providedfrom which a print material sheet 6 is fed to the print area 3 forprinting. The feeder/delivery area 2 is furthermore provided with asecond (not shown) print material roll for receiving the print materialsheet 6 returning from the print area 3 after being turned in theturning area 4, as described in detail in the following.

A plurality of rollers 8 for guiding the print material sheet 6 and aplurality of printing units 10 are provided in the print area 3. FIG. 1shows schematically seven of the rollers 8, although as a rule a largernumber are provided to convey the print material sheet 6 along anon-linear transport path through the print area 3.

FIG. 1 shows four printing units 10 so that the printing press 1 inaccordance with FIG. 1 would be suitable for four-color printing. It ishowever also possible to provide a different number of printing units10. The printing units 10 are preferably inkjet printing units, but canalso be of another digital type.

A plurality of deflecting rollers 12 and a turning unit 14 are providedin the turning area. The deflecting rollers 12 are arranged such thatthey guide the print material sheet 6 out of the print area 3 to theturning unit 14 and from the turning unit 14 back to the print area 3.The turning unit 14, which is explained in the following in greaterdetail, effects a 180° turn of the print material sheet 6 and also alateral movement of the latter. Thanks to the lateral movement of theprint material sheet 6, it is possible to guide the print material sheet6 in opposite directions through the print area 3 and the printing units10, as indicated schematically in FIG. 3. FIG. 3 here showsschematically the opposed and laterally offset movement of the printmaterial sheet 6 over a roller 8 positioned in the area of a printingunit.

FIG. 2 shows schematically a perspective view of the turning unit 14with a first turning element 20, an intermediate deflecting roller 22and a second turning element 24. FIG. 2 furthermore shows the substratesheet 6 as it is passed through the turning unit 14. The first turningelement 20 is arranged at an angle of 45° relative to an entry runningdirection of the print material sheet 6 indicated by the arrow in FIG.2, and comprises a fixed hollow tube as explained in greater detail inthe following. The print material sheet 6 is passed around the firstturning element 20 and is as a result deflected by 90°, so that afterthe deflection it runs at a right angle transversely to the entryrunning direction.

The intermediate deflecting roller 22 is a pivot-mounted deflectingroller arranged laterally offset to the first turning element 20 andextending parallel to the entry running direction of the print materialsheet 6. It is arranged such that it deflects the print material sheet6, running transversely to the entry direction after the firstdeflection, by 180°. As a result, the print material sheet runs afterdeflection in the opposite direction but still transversely to the entryrunning direction.

The second turning element 24 has the same design as the first one andis arranged at a 90° angle to it. For a lateral offset of the printmaterial sheet, the first and second turning elements 20, 24 can bearranged transversely to the entry running direction and offset relativeto one another.

The print material sheet 6 running transversely to the entry runningdirection after the intermediate deflecting roller 22 is passed aroundthe second turning unit 24 and is again deflected here by 90° so that itis again running in the entry running direction. The multipledeflections however turn the print material sheet by 180°, so that thepreviously upward-facing side now faces downwards.

The turning elements 20, 24 can have the same design, so that thefollowing describes in detail only differing embodiments of the turningelement 20.

FIG. 4 shows a schematic plan view onto the tube-like turning element20. The plan view shows in particular the area of the turning element 20wrapped around by the print material 6 during operation of the turningunit 14. The turning element 20 has in this area a surface referred toin the following as the substrate guide surface 30. In the area numbered32 of the substrate guide surface, a continuous channel structure isprovided, the design of which is described in greater detail in thefollowing. The area 32 extends approximately over the entire width ofthe turning element 20. In the circumferential direction, the area 32and hence the channel structure provided therein extends overapproximately 180° of the turning element 20. It should preferably notextend by more than 180° in the circumferential direction of the turningelement.

FIG. 5 shows a schematic plan view onto the tube-like turning element 20in accordance with an alternative embodiment. The plan view again showsthe area of the turning element 20 wrapped around by the print material6 during operation of the turning unit 14. The turning element 20 hereagain has a surface referred to in the following as the substrate guidesurface 30. In the areas numbered 45, continuous channel structures areprovided in each case, the design of which is explained in greaterdetail in the following. The areas 45 are arranged adjacently to oneanother over the width. Inside the respective areas 45, the channelstructures are continuous, i.e. all areas of the channel structure areconnected via corresponding channels of the same. There is however noconnection to the channel structures of adjacent areas 45. For this, theareas 46 are provided, which each indicate an area of the substrateguide surface 30 without channels. The substrate guide surface 30 thushas several segments or areas 45 with channel structures providedtherein and areas 46 between these without such channel structures. Theareas 45 are arranged adjacently to one another over approximately theentire width of the turning element 20. In the circumferentialdirection, the areas 45 and hence the channel structures providedtherein extend over approximately 180° of the turning element 20. Theyshould preferably not extend by more than 180° in the circumferentialdirection of the turning element.

FIG. 6 shows a schematic detailed view of a continuous channel structure60 in a substrate guide surface 30 of a turning element 20 in accordancewith a first embodiment. The channel structure 60 can be designed in theform shown both in the area 32 in accordance with FIG. 4 and in theareas 45 of FIG. 5.

The channel structure 60 has a plurality of parallel-extendingcircumferential channels 62 and a transverse channel 64 provided in thesubstrate guide surface 30. The circumferential channels 62 extend inthe circumferential direction of the turning element 20. The respectivecircumferential channels 62 are connected to one another via thetransverse channel 64, the latter centrally intersecting thecircumferential channels 62 in the circumferential direction of theturning element. It would of course also be possible to provide severaltransverse channels intersecting the circumferential channels 62 in thecircumferential direction of the turning element at different points.

The circumferential channels 62 and the transverse channel 64 have thesame depth, preferably in the range from 0.1 to 1 mm. It is however alsopossible to provide different depths for the circumferential andtransverse channels 62, 64. The circumferential and transverse channels62, 64 can for example be provided in suitable manner by means of lasermachining, etching or milling in the substrate guide surface 30. Thanksto the circumferential and transverse channels 62, 64 in the substrateguide surface 30, surface elements 70 are created between thecircumferential channels 62.

In the area of the intersection points of the circumferential channels62 and the transverse channel 64, a gas outlet opening 68 is provided ineach case in the form of a passage opening that connects the interior ofthe hollow tube to the outside, as can be easily discerned in FIG. 7.The hollow tube defines in the interior a cavity 80 limited in theradial direction by the inner wall 82. The gas outlet opening 68 extendshere from the cavity 80 into the transverse channel 64 in the substrateguide surface 30. The section shown in FIG. 7 along the line B-B fromFIG. 6 also shows one of the many circumferential channels 62. It can bereadily discerned that the circumferential channel 62 extends over 180°in the circumferential direction of the turning element, correspondingin operation approximately to the wrapped area of a print material sheet6.

The cavity 80 extends at first substantially over the entire length ofthe hollow tube. At its ends, the hollow tube can be closed in suitablemanner by end walls. At least one gas inlet opening is provided forsupplying the cavity with gas, in particular with compressed air, in theend walls and/or in a circumferential area of the hollow tube outsidethe substrate guide surface 30. This in turn allows the gas outletopenings 68 to be supplied with a gas flow.

In the longitudinal direction of the hollow tube, the cavity 80 can alsobe limited by respective slide elements (sliders), not shown. Thispermits a change in the cavity and hence a selective supply to gasoutlet openings 68, in order for example to apply gas only where thesubstrate sheet wraps around the turning element. A selective supply ofthis type is for example also possible by corresponding subdivisions ofthe cavity with individual gas supply to its subdivisions, for examplevia valves. Direct gas feed lines could also be provided for theindividual gas outlets openings, which for example can be supplied withgas individually or in groups.

FIG. 8 shows a schematic detailed view of an alternative continuouschannel structure 100 in a substrate guide surface 30 of a turningelement 20 in accordance with a second embodiment. The channel structure100 can be designed in the form shown both in the area 32 in accordancewith FIG. 4 and in the areas 45 of FIG. 5.

FIG. 8 shows a statistical distribution of one or more channels of thechannel structure 100, with the following relating to only one channel.The channel is continuous, i.e. designed such that every point insidethe channel is connected via the channel to any other point in thechannel.

The distribution of the channel forming the channel structure 100 insidethe substrate guide surface corresponds to a statistical distribution.The distribution of the channel structure 100 substantially follows auniform distribution, but can have any required distribution. Thechannel forming the channel structure 100 has a depth of preferably 0.1to 1 mm.

Gas outlet openings 68 are again provided and each open into the channelof the channel structure 100. The gas outlet openings 68 can also bestatistically distributed in the substrate guide surface. The gas outletopenings 68 preferably have a diameter of 0.3 to 0.5 mm.

FIG. 2 is intended to explain in greater detail the mode of operation ofthe turning unit 2 in accordance with the invention.

A print material sheet 6 conveyed in a first sheet conveying directionis passed around the first fixed turning element 20 and deflected due toits alignment transverse to the entry direction of the print materialsheet 6 into a second sheet conveying direction transverse to the firstsheet conveying direction. Then it is deflected by the intermediatedeflecting roller 22 into a third sheet running direction opposite tothe second one and then passed around the second fixed turning element.The alignment of the latter transverse to the third sheet runningdirection of the print material sheet 6 deflects the latter into afourth sheet conveying direction transverse to the third one. The firstand the fourth sheet conveying directions have the same orientation, andthe sheet is turned by the deflections such that the side originally ontop is now facing downwards.

During operation, gas, in particular air, is introduced into therespective cavity 80 in corresponding gas inlet openings of the turningelements 20, 24. The gas thus supplied flows via the gas outlet openings68 into the channel structure 60, 100 formed in the wrapped area of thesubstrate guide surface 30. The gas spreads substantially evenly via therespective channels 62, 64 over the substrate guide surface 30 and formsa uniform air cushion between the substrate guide surface 30 and theprint material sheet 6. A gas flow thus distributed creates an aircushion which extends over the entire substrate guide surface 30. Theprint material 6 is thus deflected with reduced friction into therespective second or fourth sheet conveying direction. By selectivecontrol of the areas 45 or also of individual gas outlet openings 68,the gas flow can be limited substantially to the wrapping area of theprint material sheet.

The first and second turning elements 20, 24 are as already mentionedarranged fixed, so that the print material 6 is always passed around thesame circumferential area of the turning elements 20, 24.

The turning unit can turn a print material sheet printed on one side inthe print area 3 in the manner stated above and make it available forverso printing.

The invention was described on the basis of preferred embodimentswithout being restricted to these.

1. Turning unit for a substrate sheet with at least one turning elementhaving the following: a basic body with an outer, round substrate guidesurface angled relative to a sheet conveying direction; a channelstructure provided in the substrate guide surface, wherein the channelstructure has channels distributed statistically in the substrate guidesurface; and a plurality of gas outlet openings opening onto the channelstructure and which can be supplied with gas in order to provide a gasflow towards the channel structure.
 2. The turning unit according toclaim 1, wherein at least two turning elements arranged angled relativeto a sheet conveying direction and to one another.
 3. (canceled)
 4. Theturning unit according to claim 1, wherein at least some of the gasoutlet openings open onto at least one transverse channel.
 5. (canceled)6. The turning unit according to claim 1, wherein the substrate guidesurface has a plurality of separate channel structure segments with arespective channel structure arranged adjacently over a width of thesubstrate guide surface, where a respective channel structure is influid communication with at least one gas outlet opening.
 7. The turningunit according to claim 1, further including a control unit which isable to supply gas to the gas outlet openings individually or in groups.8. The turning unit according to claim 1, further including a cavityinside the basic body which is in fluid communication with the gasoutlet openings and which can be supplied with gas.
 9. The turning unitaccording to claim 8, further including at least one slide in thecavity, the slide being movably mounted such that it permits selectivesupplying of gas to gas outlet openings via the cavity.
 10. The turningunit according to claim 9, wherein two sliders are provided that aremovable from opposite ends into the cavity.
 11. The turning unitaccording to claim 7, characterized by a plurality of valves forindividual or grouped supply of gas to gas outlet openings.
 12. Theturning unit according to claim 6, wherein the gas inlet opening(s)associated with a respective channel structure segment can be suppliedwith gas in groups.
 13. The turning unit according to claim 1, whereinthe channel structure extends over a maximum of 180° in thecircumferential direction of the substrate guide surface.
 14. Theturning unit according to claim 1, wherein the channel structure has adepth of 0.1-1 mm.
 15. The turning unit according to claim 1, whereinthe gas outlet openings have a diameter of 0.3-0.5 mm.
 16. (canceled)17. Turning unit for a substrate sheet with at least one turning elementhaving the following: a basic body with an outer, round substrate guidesurface angled relative to a sheet conveying direction; a channelstructure provided in the substrate guide surface, wherein the channelstructure has a plurality of circumferential channels spaced apart andextending in the circumferential direction of the round substrate guidesurface, and at least one transverse channel extending transversely tothe circumferential channels and being in fluid communication with atleast two circumferential channels; and a plurality of gas outletopenings opening onto the channel structure and which can be suppliedwith gas in order to provide a gas flow towards the channel structure.18. The turning unit according to claim 17, wherein at least some of thegas outlet openings open onto at least one transverse channel.
 19. Theturning unit according to claim 17, further including a control unitwhich is able to supply gas to the gas outlet openings individually orin groups.
 20. The turning unit according to claim 19, wherein the gasinlet opening(s) associated with a respective channel structure segmentcan be supplied with gas in groups.
 21. The turning unit according toclaim 17, further including a cavity inside the basic body which is influid communication with the gas outlet openings and which can besupplied with gas.
 22. The turning unit according to claim 21, furtherincluding at least one slide in the cavity, the slide being movablymounted such that it permits selective supplying of gas to gas outletopenings via the cavity.
 23. The turning unit according to claim 17,wherein the channel structure extends over a maximum of 180° in thecircumferential direction of the substrate guide surface.
 24. Theturning unit according to claim 17, wherein the channel structure has adepth of 0.1-1 mm.
 25. The turning unit according to claim 17, whereinthe gas outlet openings have a diameter of 0.3-0.5 mm.